Motorcycle frame



Dec. 26, 1950 w, LECHMERE 2,535,540

MOTORCYCLE FRAME Filed July 9, 1948 mvsn'ron AGENT Patented Dec. 26,1950 UNITED STATES PATENT OFFICE Walter F. Lechmere, Birmingham,England, as-

signor to The James Cycle Company Limited, Birmingham, EnglandApplication July 9, 1948, Serial No. 37,831 In Great Britain February 3,1948 3 Claims. 1 This invention relates to motor cycle frames. In motorcycle frames hitherto proposed or known it is usual to mount the stem orother supporting element of the front fork assembly in a short length oftube or a casting which forms a component part of the frame. In the mostcom moo form of construction this tube is secured to the other framemembers at each end by an assoelated lug presenting a pair of circularopenings into one of which the tube extends and into the other of whichextends a member of the frame, the lug and the tube and the lug and theframe being secured to each other by welding or brazing and the lugbeing customarily formed as a casting or forging or sometimes of foldedsheet metal.

One object of the present invention is to provide a new or improvedconstruction of mounting member for the front fork assembly which issimpler and less expensive to manufacture.

A further object of the present invention is to providea new combinationof front fork assembly mounting member and frame construction which isof great strength and at the same time simple and inexpensive tomanufacture.

Referring to thedrawingsz Figure 1 illustrates a motor cycle frameconstructed in accordance with the invention includmg a mounting memberfor the front fork assembly also constructed in accordance with theinventlon, the whole being shown in "Side elevation.

Figure 2 is a fragmentary view of the construction shown in Figure 1showing in side elevation the position of attachment of the mountingmember on the motor cycle frame.

Figure 3 is a plan view of the parts shown in Figure 2.

Figure 4 is a cross sectional view on the line 4-4 of the parts shown inFigure 2.

Figure 5 is a perspective view of the mounting member alone.

Figure 6 is a view of the sheet metal blank constituting one of theelements from which the mounting member is constructed and is shownprior to folding.

Figure 7 is a fragmentary view of the lower end of the mounting membershown in section on the line 1- of Figure 2.

As seen in Figure 1 the motor cycle frame comprises-at the rear a saddletube In of usual construction secured at each end by lugs H and I2 alsoof usual construction to conventional rear frame members I 3 and M. Theposition of the rear wheel of the motor cycle is indicated by the chaindotted lines IS.

The front portion of the frame is formed of asingle length of tubesecured at one end to the upper portion of the saddle tube by means ofthe lug II and at the other end to the lower portion of the saddle tubeby means of the lug 52.

Between the lugs H and i2 this front portion is bent into loop formationand comprises an upper approximately horizontal length 16 and a lowerapproximately 'horiztonal length I I, each of these lengths extendingforwardly from respective upper and lower portions of the saddle tubelugs H and H. The forward ends of the lengths l6 and ii are connected bya forwardly disposed length of tube ii! which merges with the length 48through a rounded corner or arcuate portion IS.

The mounting member for the front fork assembly seen generally at '20,Figure 1, comprises a length of tube 2! which is adapted to receivecomplementary supporting elements of the front fork assembly. Forinstance as seen in Figure '7, the ends of the tube may be bored out toa larger internal diameter as at 22 compared with the central portion ofthe tube as at 23, an internal axially directed shoulder 24 therebyexisting at each end of the tube and forming in conjunction with themachined portion 22 a housing for the bearings on the front forkassembly constituting the supporting elements therefor.

A further part of the mounting member comprises a plate which is shownin Figure 6 in the form of a blank prior to its application to the tube2!. The plate comprises a central portion indicated generally at 25which is bent round to part cylindrical form so as to embrace the frontportion 25 of the circular cross section tube 2|.

The length of the plate may be such that it is equal to the length ofthe tube and in applying it to the tube it is arranged so that its upperand lower edges 21 and 28 of the central portion are flush withcorresponding ends of the tube as seen in Figures 2 and 5, oralternatively the plate may be initially somewhat longer than the tubeand the upper and lower edges may be subjected to a machining operationafter application to the'tube 2| so as to obtain a flush relationbetweenthe ends of the tube and the edges 21 and 28; of the plate.

At either side of the central portion the plate has side portions 25 and39 as seen in Figure 6 and these are folded towards each other and aredirected rearwardly on either side of the tube 2| and extendtangentially of the walls of the tube 2| and substantially parallel toeach other as best seen in Figure 4.

Each side portion is provided at its upper edge with an ear 3| and atits lower edge is an ear 32 which, after the side portions have beenfolded towards each other are bent inwardly so that the inner edges 33of the upper ears and inner edges 34 of the lower ears lie adjacent eachother.

The edges 35 of the upper ears and the edges 36 of the lower ears are ofsuitable concave formation corresponding with the external curvature ofthe tube 2| so that after bending inwardly, they lie closely against theouter wall of the tube. Also the line along the edge of the upper andlower ears is bent as indicated by the dotted lines 31, Figure 6, and ispreferably spaced inwardly from the corresponding edges 2'! or 28 of thecentral portion of the plate, the ears being separated from the edges2'! and 28 by small open-ended slots 38 so that after bending, the earsl'e in a plane spaced inwardly from the ends of the tube and engage theside walls of the tube at positions spaced inwardly from the endsthereof.

After applying the plate folded and bent as described to the tube 2i itis suitably welded or brazed to the tube as for instance by applying afillet weld along the tangential junction of the tube 2| and the sideportions 29 and 38. Adjacent edges 33 and 34 of corresponding ears arealso welded or brazed together.

As applied to the forwardly disposed tu ular member of the motor cycleframe including a rounded corner portion l9 as described, the rear edges39 of the side portions are preferably of concave formationcorresponding with the curvature of the arcuate portion IQ of the frameand the width of the side portions is such that the concave edges lielevel with the axis or centreline of the tubular member of the frame towhich the mounting member is applied. The edges 48 and 4| of upper andlower ears respectively are also of suitable concave formation so thatin the bent position of the ears these edges lie closely against thearcuate portion IQ of the frame.

The arcuate portion ill of the frame is engaged with the nternal sidewalls of the cavity defined by the side portions 22 and 88 and the ears3| and 32 of the plate and is suitably Welded or brazed The axis of thetube 2| extending downwardly and somewhat forwardly to correspond withthe steering axis of the motor cycle. The front fork assembly is shownin position at 42 by the dotted lines in Figure l.

Preferably the plate of the mounting member includes an opening in thecentral portion which as seen in the drawings at 44-, may be of ovalform. This opening in the blank may be used for the insertion of a nameplate or transfer and is found also to facilitate the folding of theblank around the tube 2|.

In the upper part of the side portions 29 and 35 means are includedwhereby the tank of the motor cycle may be secured at its forward end,

sad means comprising a pair of circular holes 43 extending through thematerial on the plate.

Although in the claims which follow the term welding is employed todenote the method of securing the plate to the tube of the front forkassembly mounting member, and the method of securing the plate to themotor cycle frame, it will be understood that it is within the scope ofthe invention to employ brazing to effect such securing.

What I claim then is:

1. In a motor cycle frame the combination of a main frame of loopedformation in which the upper and forward members are formed of a singlelength of tube and merge into one another through an arcuate portion,with a mounting member for the front fork assembly comprising a bearingtube and a folded sheet metal plate having a part-cylindrical centralportion embracing the tube and welded thereto, and rearwardly directedside portions on each side of said tube extending tangentially andsubstantially parallel to each other from the walls of said tube todefine a cavity into which the arcuate porton of the frame engages, thearcuate portion being positioned in substantially tangentialrelationship to said bearing tube, and being welded to said sideport'ons of the sheet metal plate.

2. In a motor cycle frame in which a mounting member for a front forkassembly is welded to a tubular arcuate member joining the upper andforward members of the frame, the mounting member comprises a bearingtube and a folded sheet metal plate having a part-cylindrical centralportion embracing the front portion of the tube, rearwardly directedside port'ons on each side of the tube extending tangentially andsubstantially parallel to each other from the walls of the tube, saidside portions being connected together at their upper and lower edges byintegrally formed ears, the rear edges of which are of concave arcuateform, so that said side portions and ears define a hollow body adaptedto receive the arcuate member of the frame in contact with the innerside walls of said body and with the rear edges of said ears.

3. In a motor cycle frame in which a mounting member for a front forkassembly is welded to a tubular arcuate member joining the upper andforward members of the frame, the mounting member comprises a bearingtube and a folded sheet metal plate having a part cyl ndrical centralportion embracing the front portion of the tube, and rearwardlydirected-side portions on each side of the tube extendin tangentiallyand substantially parallel to each other from the walls of the tube,said side portions having rear edges of arcuate form corresponding withthe curvature of sad arcuate member of the frame and substantially levelwith the axis of the arcuate member.

W. F. LECHMERE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain 'Apr. 21, 1932

